Natural gas is a fossil fuel with a low output of carbon dioxide (CO2) and with a low emission of waste products during combustion. Its contribution as one of the most important world energy resources rises continually. Against the background of a shortage of raw materials and of the constantly growing demand for energy and for reasons of environmental protection, the treatment and utilization of natural gas therefore afford a very promising possibility for the efficient and low-emission generation of energy.
However, the direct utilization of crude natural gas has hitherto been possible to only a limited extent. On account of the acid constituents of a natural gas stream, such as, in particular, hydrogen sulfide (H2S), these often cannot be used directly in a gas turbine or for pipeline transport. Acid natural gas streams are therefore for the most part burnt off, unused.
Alternatively to this, attempts are made to treat natural gas for further utilization by means of various separation techniques. For this purpose, physical or chemical absorption media are employed in order to ensure that natural gas has the purities required for further use. In general, however, in this case only the fraction of hydrogen sulfide and of carbon dioxide in the crude natural gas is separated off and recovered. The CO2 contained in the exhaust gas occurring during subsequent combustion or the SO2 obtained from the hydrogen sulfide during combustion is frequently left unused.
So that the components contained in the exhaust gas or in what is known as flue gas can also be separated off and utilized, for example, before combustion, the hydrogen sulfide is first removed from the crude natural gas and carbon dioxide contained in the flue gas is separated off in a method carried out after combustion. However, two methods separate from one another and the corresponding techniques are necessary for this purpose, as a result of which the investment costs for a new construction and/or for the retrofitting of existing plants are high.